The tool steels are categorized as shown in Figure 1. Steels are
categorized by quench and application. Those categorized by quench are shown as
follows:
- W1 to W5 = Low-temperature hardening with water quench
- O1 to O7 = Low-temperature hardening with oil quench
- A2 to A9 = Higher-temperature, high-alloy air hardening
The steels that are categorized by application are:
1. Shock-resisting steels:
-
S1 to S7 = Shock-resisting tool steels
2. Hot-work tool steels:
- H (Chromium) H10 to H19 = Hot-work die steel with high
operating temperature as well as high hardening temperatures with complex
quenching
- H (Tungsten) H21 to H26 = Hot-work tool steels with higher
operating temperatures and high hardening temperatures plus complex quenching
- H (Molybdenum) up to H42 = same as H21 to H26
3. Dimensionally stable tool steels:
- D2 to D7 = High-carbon, high-chromium cold-work tool
steels with a high austenitizing temperature and complex quenching
4. High-speed cutting tool steels:
-
HSS (tungsten) = T1 to T15 complex steels designed for
high-speed cutting
- HSS (molybdenum) = M1 to M36 complex steels designed for high-speed
cutting
- HSS (ultra-hard) = M41 to M47 complex steels designed for high-speed
cutting
5. Special Purpose (low-alloy)
steels:
- L2 to L6 = Low-alloy, special-purpose tool steels
6. Mold steels:
-
Mold steels = P2 to P21 usually low-carbon and used often
for cold hobbing of the impression on coining dies, then carburized or
sometimes nitrided
The next part in this series will begin to focus in on the different tool steels
and their heat treatments.
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